The present invention relates to tires. More particularly, it relates to the arrangement of reinforcing filaments in the beads, and more generally, deals with the design of the carcass.
Tire carcass reinforcements usually consist of one or more plies, currently usually radial plies, wrapped around one or more bead wires arranged in the beads. The beads constitute the means that allow the tire to be fixed to the wheel rim. The fact that the carcass reinforcements consist of plies means that these need to be produced by calendering and then cutting them at the desired angle (90.degree. to the direction of the filaments for a radial carcass) into pieces of the desired length, these pieces then being joined together by welding parallel to the filaments. All these operations constitute separate preparatory steps in the actual assembly of the tire. The existence of these preparatory early steps makes managing work flow through manufacturing shops more complicated.
It has already been proposed that tire carcasses be produced from a single filament. The difficulty in this case lies in designing carcasses which are durable enough to fulfill their function of being a structure that reinforces the tire and which, by the path taken by the carcass filament, are as easy as possible to produce in a mechanized way.
As an illustration, the proposals contained in patents U.S. Pat. No. 4,277,295 and U.S. Pat. No. 5,308,432 may be mentioned. However, mechanizing the movements of a laying member that carries out the first of these proposals is not simple. Furthermore, having knots or crossing filaments in the bead of the tire is advised against because the tension of the filaments in this region is considerable. As regards the second proposal, it has the drawback of the difficulty in transferring the reel from one line to the other on each side of the tire. Furthermore, given the necessarily non-zero bulk of the members that move the reel, and given the bulk of this reel, it is not possible either in the first proposal or in the second for the last carcass-reinforcing arches to be laid with said reel continuing the same movement. The problem is that at the end of laying, the mechanism comes up against the first arches laid well before the last ones have been laid, this point being reached all the earlier, the bulkier the reel.
In practice, a reel of this kind is quite bulky. It is therefore difficult to make it accelerate a great many times because of its weight and its inertia, and it is difficult to make it run around the bead wire because the space available is small, especially if the tire is manufactured on a former which more or less corresponds to its future internal volume, this being especially true if the bead wire is close to the end-position it will occupy in the finished tire.